package com.njupt.HashTable;

import java.util.*;

public class FourSum {

    public List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>> result = new ArrayList<>();
        Arrays.sort(nums);

        for (int i = 0; i < nums.length; i++) {
            if(nums[i]>target && nums[i] > 0){
                //
                break;
            }
            if(i>0 && nums[i] == nums[i-1])
                continue;

            for (int j = i+1; j < nums.length; j++) {
                if(nums[j] + nums[i]> target && nums[j] + nums[i] > 0){
                    break;
                }

                if(j>i+1 && nums[j]== nums[j-1])
                    continue;
                int left = j+1;
                int right = nums.length-1;
                while(left < right){
                    int num = nums[i] + nums[j] + nums[left] + nums[right];
                    if(num>target){
                        right--;
                    } else if (num<target) {
                        left++;
                    }else {
                        result.add(Arrays.asList(nums[i],nums[j],nums[left],nums[right]));
                        while(left<right && nums[left] == nums[left+1]) left++;
                        while(left<right && nums[right] == nums[right-1]) right--;
                        left++;
                        right--;
                    }
                }
            }
        }
        return result;

    }

    public static void main(String[] args) {
        int[] nums = {2,2,2,2,2};
        FourSum test = new FourSum();
        List<List<Integer>> lists = test.fourSum(nums, 8);
        Iterator<List<Integer>> iterator = lists.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }


}
